1. Field of the Invention
The present invention radiates electron-beam into the free atmosphere and discharges electric energy to grounded targets.
2. Description of the Prior Art
Nonvacuum electron beam has applications including metallurgical heat engineering and directed energy concepts. Energetic beams are preferred for projection into the atmosphere, and similar high-pressure gaseous media, due to their penetrating depth and spatial stability. In addition, large beam current is desired as the resulting plasma focussing action radially confines the beam, and reduces dispersion. The approximate range R, in centimeters, at sea level, of an electron whose energy E, in units of MeV, lying between two and one-half and twenty million electron volts, is given by Feather's rule as EQU R=543(E)-106.
Thus, an electron whose energy is 5 MeV penetrates a maximum of some twenty-five meters into the atmosphere as its energy is expended ionizing the air.
The electron range is inversely porportional to the frequency of the ionizing interactions, and so greater range is obtained in media of lower density. By way of example, the electron's range is approximately doubled by reducing the density of the absorbing media by a factor of one-half.
A low density ionized channel is formed by repetitively discharging electron beam into the atmosphere. Each beam penetrates further owing to the rarefraction provided by the heating of its predecessors. This directed energy technique is known in the art as hole boring. Depending upon beam power and repetition rate, beam ranges can be obtained that exceed, by manyfold, the range of a single pulsed beam.
A discussion of hole boring is presented in F. Winterberg, "The Potential of Electric Cloud Modification by Intense Relativistic Electron Beams," Zeitschchrift fur Meteorologie, Vol. 25, No. 3, pp. 180-191, (1973). Winterberg suggests a pulse power in combination with a repetition rate to produce a grand maximum electron beam range in the atmosphere. The suggested repetition rate is one million beams per second. The rate is high because the lifetime of long channels is short, due to heat loss from their large surface area. The next beam must be discharged into the channel before appreciable density is recovered due to cooling.
Repetition rates such as a million beams per second are a thousandfold beyond current art in high-voltage switch technology. A technique is needed to improve the economy of beam energy transport, thereby increasing electron beam range, using presently obtainable pulse repetition rates such as a hundred per second.